There are many times in the industrial process where it is advantageous to know the thicknesses (physical properties) of the material that is being produced. In the case of multilayered plastics or coated cloths and papers, substantial savings of materials may be achieved if the thickness of the layers and coatings may be kept consistent and to a specific minimum. Additionally, solvents and coatings that are kept at the correct physical makeup may be applied in a consistent, measurable manner.
Currently in industrial processes there is no consistent manner to determine multilayer thicknesses of materials. Existing systems such as Beta gauges can determine total thickness of a material and use this as a base to calculate the approximate thickness of a coating. This method however requires multiple devices to first determine the average thickness of the base material and then subtract that measurement from the average total thickness to determine the coating thickness. Additional methods are being developed that use infrared technology to determine the total thickness of a material but this method does not allow for multilayer measurements of the material.
Furthermore, there are many times in the industrial process where it is advantageous to know the integrity of the seal on a product. Seal integrity is crucial in any case of a pouch that contains food, medical supplies, or any container in which contamination would compromise the contents. Substantial savings of materials due to scrap and downstream product waste may be achieved if the seal integrity and viability is available in a real time production environment. Of even more importance to some organizations is the reduction in risk due to continuous inspection of products.
Currently in industrial processes there is no consistent manner to determine seal integrity. Existing quality assurance systems primarily consist of off-line, random sampling systems. Testing may include filling product with air and then submerging in liquid to observe leaks, or where product is torn apart with a device that measures the force required to separate a seal. Other methods are based strictly on visual observation either by a mechanical device or human observation. Because of the random nature of these tests, many improperly sealed containers may be produced without the knowledge of the producing entity.
Methods of measuring thickness of a material using interferometric devices are known in the prior art. For example, U.S. Pat. No. 6,038,027, (Marcus et al.) and U.S. Pat. No. 6,067,161, (Marcus et al.), of which the entire disclosure of these patents is hereby referenced; concern the Method and Apparatus for determining a thickness profile of a moving material having at least two optical interfaces. These patents use an interferometric device and present an apparatus to maintain some consistency to the measurements obtained from the moving web but don't account for an in-process production system or the corresponding feedback to the processing controls of a production system. These patents also fail to use devices in the determination of seal integrity.
The present invention uses improvements to the interferometric device and the corresponding algorithms to improve data acquisition and measurement usablilty, and to accurately measure and predict seal integrity as a function of material thickness, misshapen seals, air and liquid gaps, and other characteristics that constitute a bad seal. The invention also incorporates multiple probe/optical sensor locations and purposes within a single system to provide complete process interpretation, feedback and control.
Various methods exist as part of the present invention for accommodating the movement of the web as it passes the measurement area. Some packaging systems require stages that transverse the web in a lateral fashion to measure the complete width, while others only measure single points along the moving web. The present invention will incorporate locations of multiple probes/optical sensors based on the specific equipment being attached to, and the container or pouch being measured, and these probes/optical sensors may be linked via optical switches to accomplish this measurement task.